For the lavender flowers, heat the water and caster sugar together in a pan.
Stir until the sugar melts and then boil steadily, so that the liquid can reduce a little.
Take the pan off the heat and leave to cool.
When the sugar has cooled, add the lavender flowers to the pan.
For the panna cotta, line six ramekins with cling film and place on a tray. Warm three quarters of the cream with the vanilla sugar and orange zest in a pan, taking care not to boil the cream.
Strain the mixture through a sieve into a mixing bowl.
Sprinkle the gelatine over two tablespoons of water until it becomes spongy. Heat very gently in a clean pan over a low heat until it dissolves.
Add the cream mixture to the gelatine and take off the heat. Leave to cool.
Softly whip the remaining cream and add the cream to the mixture.
Pour the mixture into the lined ramekins and transfer to the fridge to chill.
Chill for at least two hours until set.
Turn the panna cotta out onto individual serving plates and drizzle the lavender syrup over them. Decorate with the sugary lavender flowers.